The human pathogen Streptococcus pneumoniae is an infectious agent responsible for millions of deaths world- wide a year, particularly among the young and the elderly, and is the leading cause of multiple diseases, including bacterial pneumonia, sepsis, and meningitis. The virulence of these Gram-positive bacteria is increased by pili, elongated fibrous structures on their surface that mediate intercellular adhesion during the colonization process. Class C sortase enzymes (SrtC) are the architects of pili, and they function by recognizing and covalently linking pilin subunits to one another. This direct link between SrtC activity and infection therefore presents an exciting new antibacterial target for pneumococci strains that are resistant to conventional therapeutics. In this appli- cation, I propose a series of biomolecular simulations that address both the long-range association and local, induced-fit binding mechanisms of the pilin subunit recognition mechanism by each of the three S. pneumoniae SrtC proteins, important initial steps in the assembly of pili. Data resulting from these studies will prove invaluable in future structure-based drug design efforts that target SrtC. Results will also lay a foundation for my long term goal of developing a complete model of the pilin assembly process that would resolve discrepancies in the available experimental data concerning this process. Receipt of the K22 award will provide support in not only accomplishing these scientific goals, but will also greatly benefit my future independent biomedical career. My long term goals involve building a vibrant, productive research group at a Tier 1 research university that uses theoretical and computational techniques, in strong collaborations with experimentalists, to address and advance our understanding of issues important to public health. In this proposal I present a career development plan that will guide my transition from a mentored to an independent scientist that focuses on the development of technical and non-technical skills that will be important for my future career as an assistant professor. I anticipate using the two years of support provided by this grant to lay the scientific foundation necessary for creating future competitive applications, including other junior faculty awards and an R01 grant.